This invention relates to a process and an apparatus for generating exposure masks made up of at least two reduced-size images of recording originals, which reduced-size images are precisely positioned with respect to one another. Such exposure masks are, for example, useful for producing a high density storage medium such as a multicolor micro-image.
Exposure masks of the type described above are used, for example, in the production of multicolor micromaps. From multicolor original maps (for example on the scale of 1:50,000) color separations in the form of negative film originals (for example separate separations for black, red, green, and blue portions of the map) are made for each other. These negative film originals are then reproduced in reduced form individually on photosensitive micro-original carriers of glass. After being developed, the micro-original carriers are vapor-treated with a chromium layer, and then remaining portions of the photosensitive layer are removed along with the overlying chromium layer. These positive micro-originals are then used to produce negative micro-originals by contact copy.
If, for example, a map formation of several adjacent original maps (for example 5.times.5=25 maps) is to be recorded on a recording carrier or substrate, then the corresponding negative micro-originals for each color must be manually adjusted and positioned with respect to one another in the recopying step, so that a negative micro-original of the entire map formation is obtained for each color. First, the negative micro-originals of the black or background separation, for example, are adjusted and positioned crosswise from the center of the original formation, and then the other negative micro-originals are positioned with respect to one another and copied. For this purpose, there are required at least six copying or vapor treatment steps.
From the positive original formation thus obtained for the production of the exposure masks for the remaining colors, in each case a negative original formation is created. On this negative original formation retouching techniques are used to remove all the details down to the index marks in the form of corner markings of the individual originals (in topographical maps the so-called sheet corners). The color separations are then adjusted into place and copied.
The production of exposure masks by the process described above requires about 225 copying steps (coating with a photosensitive layer, exposing and developing the photosensitive layer, and vaporizing with a chromium layer) and about 204 micro-original carriers of glass of high surface quality to produce a map formation of 25 maps.